Dressing of moulds for castings and ingots



United States Patent s 131 443 onrssmo or tuburins non CASTHNGS AND moors This invention relates to the dressing of sand moulds used in the production of castings and ingots.

The normal method of making a sand mould is to compact the sand against a pattern but before doing so it is customary to apply to the surface of the pattern a so-called release composition in order that the pattern shape should afterwards be removable from the sand. The release composition is usually essentially hydrophobic and may be for example a dispersion of a fatty substance such as a fatty acid in a mineral oil. It normally arises in this procedure that some of the release composition is retained on those surfaces of the sand mould which have been in juxtaposition with the pattern.

When molten metal is poured into a mould as thus prepared, and allowed to set therein, to form a casting or ingot it is of course necessary that the solidified ingot or casting should be easily removable from the mould and desirable that it should have a good surface finish. It is the customary practice therefore to apply a so-called mould dressing to the surfaces of the mould which are to be contacted by the molten metal. Such mould dressings are broadly speaking of two main types, those based on water which must be dried out on the surface of the mould, and those based on alcohol or other volatile solvent which may be dried out by evaporation, or the solvent removed by burning it olf.

Of these two types of mould dressing, those based on an aqueous medium have the advantage of being considerably more economical. The difliculty arises, however, that if the surface of the mould has, as indicated above, picked up some of the hydrophobic release composition which was originally on the surface of the pattern, then the surface of the mould acquires a substantial degree of water-repellency. Accordingly, it repels the application of a waterbased mould dressing, and it may frequently be necessary in such circumstances to resort to the use of the more expensive type of alcoholsbased dressing.

1-: is an object of the present invention to overcome this difliculty by providing a release composition for application to the original pattern which minimizes or eliminates the risk of water-repellency on the surface of the compacted sand mould.

According to the present invention there is provided a method for the production of sand moulds for use in the production of an ingot or casting which comprises compacting sand to the shape of the desired mould against a pattern which carries a thin coating of a release composition which is a solution, in a light mineral oil (e.g. paraffin oil), of a mineral oil emulsifying agent.

According to a further feature of the present invention there is provided a method for the production of a sand mould which is surface-conditioned to receive molten metal for the formation of an ingot or casting which comprises forming a sand mould by the method which is set forth and applying to the surfaces of the mould which are to contact the molten metal a water-based mould dressing known per se.

It will be understood that the expression sand mould used in this application includes not only moulds which have a cavity into which molten metal can be poured but also sand cores which may form part of such moulds.

Ihe emulsifying agent present in the release composilice.

tion may be any of those which are commonly known in the art, and marketed for use in the production of oilinwater or water-in-oil emulsions; non-ionic dispersing agents which are condensation products of ethylene oxide with long chain alkyl alcohols are generally very suitable. Such products are commercially available, e.g. under the trade mark Empilan =A, produced by Marchon Products Limited. This material is a liquid anhydrous non-ionic emulsifying agent and is specifically designed for the conversion of mineral oil-s into selfemulsifying agents. Thus, for example, about 1 0% of Empilan A is dissolved in mineral oil by stirring, and the mixture poured slowly with stirring into water, a stable emulsion is obtained. It has been found for example that a 1% solution of Empilan A in 99% of kerosene forms a release composition which allows ready separation of the pattern from the sand mould during the production of the sand mould but which, nevertheless, permits the use of water-based mould dressings applied to the mould surface before the pouring of the molten metal.

Although, as indicated above, even as low a proportion as 1% by weight of an emulsifying agent gives useful results, substantially higher proportions may be used, e.g. up to 20% by weight of the total composition.

lit is to be noted that while the release compositions of the present invention are of especial value where waterbased mould dressings are to be used, nevertheless they may also be employed satisfactorily when spirit-based mould dressings are employed. Further it has been observed that until water is applied to its surface the layer of emulsifying agent itself is a good stripping medium and lubricant, resembling a fatty acid in its properties.

The following example illustrates the application of the invention to a practical case.

Example In the production of an iron ingot mould the mould was produced as a casting in a sand mould. The sand core (which defined the inner shape of the casting cavity of the iron mould ultimately produced) was 10 feet long and of maximum diameter 3 feet. It was produced in a core box of which the surfaces against which the sand was compacted were .pre-treated by the application of a release composition.

Before being put to use the resultant sand core was given a surface coating of a mould dressing of 10 lbs. of crushed carbon per gallon of water containing 2% by weight of sulphite lye. It was found that the most convenient way of applying this dressing was to stand the core on its end and pour the dressing over it from the top so that the dressing flowed down the sides.

It was found that when a conventional release composition was used on the core box consisting of a dispersion of a fatty acid in nuner-al oil, suflicient of that release composition was retained on the surface of the sand core as to produce substantial patches of highly hydrophobic properties which were not easily wet-ted by the water-based mould dressing which is referred to. It was accordingly necessary to spend considerable time in swabbing and brushing the dressing onto these areas in order that the whole core surface should be adequately dressed.

However when the release composition used in the core box was substituted by a 1% by weight solution in paraffin oil (kerosene) of a condensation product of ethylene oxide and along chain fatty alcohol, equally good release properties were obtained and it was found that the said water-based mould dressing spread evenly over the sand core leaving no bare patches due to any local areas of hydrophobic surtace.

What I claim is:

1. A method for the production of sand moulds which are surface-conditioned to receive molten metal for the 4% fonnation of ingots :and castings which comprises eom- Refesenees Clte in the file of this patent pacting sand to the shape of the desired mould against a UNITED STATES PATENTS pattern which carries a than coating of a release oomposition which is a solution, in a light mineral oil, of a min- 1:614:846 More 1927 enal oil emulsifying agent and applying to ihe surfaces 5 1,845,371 Wallace 1932 of like mould which are to contact the molten metal a FOREIGN PATENTS water-based mould dressing.

I l 579,218 Canada July 7, 1959 2. A method aeeordlng .to claim 1 wherom the mould 831,162 Great Britain Mar 23, 1960 dressing is an aqueous dispersion of carbon particles. 

1. A METHOD FOR THE PRODUCTION OF SAND MOULDS WHICH ARE SURFACE-CONDITIONED TO RECEIVE MOLTEN METAL FOR THE FORMATION OF INGOTS AND CASTINGS WHICH COMPRISES COMPACTING SAND TO THE SHAPE OF THE DESIRED MOULD AGAINST A PATTERN WHICH CARRIES A THIN COATING OF A RELEASE COMPOSITION WHICH IS A SOLUTION, IN A LIGHT MINERAL OIL, OF A MINERAL OIL EMULSIGYING AGENT AND APPLYING TO THE SURFACES OF THE MOULD WHICH ARE TO CONTACT THE MOLTEN METAL A WATER-BASED MOULD DRESSING. 